Writing instrument



FIG. 1 is front elevation view;

FIG. 2 is a rear elevation view;

FIG. 3 is a side elevation view from the right of FIG. 2;

FIG. 4 is a side elevation view from the left of FIG. 2;

FIG. 5 is a perspective view;

FIG. 6 is a top view; and,

FIG. 7 is a bottom view. 

The ornamental design for a writing instrument, as shown and described. 